package com.tunan.utils;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class DateUtils {
	      
	    static final String formatPattern = "yyyy-MM-dd";  
	      
	    static final String formatPattern_Short = "yyyyMMdd";  
	      
	      
	    /** 
	     * 获取当前日期 
	     * @return 
	     */  
	    public static String getCurrentDate(){  
	        SimpleDateFormat format = new SimpleDateFormat(formatPattern);        
	        return format.format(new Date());  
	    }  
	      
	    /** 
	     * 获取制定毫秒数之前的日期 
	     * @param timeDiff 
	     * @return 
	     */  
	    public static String getDesignatedDate(long timeDiff){  
	        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
	        long nowTime = System.currentTimeMillis();  
	        long designTime = nowTime - timeDiff;         
	        return format.format(designTime);  
	    }  
	      
	    /** 
	     *  
	     * 获取前几天的日期 
	     */  
	    public static String getPrefixDate(String count){  
	        Calendar cal = Calendar.getInstance();  
	        int day = 0-Integer.parseInt(count);  
	        cal.add(Calendar.DATE,day);   // int amount   代表天数  
	        Date datNew = cal.getTime();   
	        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
	        return format.format(datNew);  
	    }  
	    /** 
	     * 日期转换成字符串 
	     * @param date 
	     * @return 
	     */  
	    public static String dateToString(Date date){  
	        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
	        return format.format(date);  
	    }  
	    /** 
	     * 字符串转换日期 
	     * @param str 
	     * @return 
	     */  
	    public static Date stringToDate(String str){  
	        //str =  " 2008-07-10 19:20:00 " 格式  
	        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
	        if(!str.equals("")&&str!=null){  
	            try {  
	                return format.parse(str);  
	            } catch (ParseException e) {  
	                // TODO Auto-generated catch block  
	                e.printStackTrace();  
	            }  
	        }  
	        return null;  
	    }  
	      
	    //java中怎样计算两个时间如：“21:57”和“08:20”相差的分钟数、小时数 java计算两个时间差小时 分钟 秒 .  
	    public void timeSubtract(){  
	        SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   
	        Date begin = null;   
	        Date end = null;   
	        try {   
	        begin = dfs.parse("2004-01-02 11:30:24");   
	        end = dfs.parse("2004-03-26 13:31:40");   
	        } catch (ParseException e) {   
	        e.printStackTrace();   
	        }   
	  
	        long between = (end.getTime() - begin.getTime()) / 1000;// 除以1000是为了转换成秒   
	  
	        long day1 = between / (24 * 3600);   
	        long hour1 = between % (24 * 3600) / 3600;   
	        long minute1 = between % 3600 / 60;   
	        long second1 = between % 60;   
	        System.out.println("" + day1 + "天" + hour1 + "小时" + minute1 + "分"   
	        + second1 + "秒");   
	    }  
	  
	}  
